Publications by authors named "Kevin Berger"

High temperature superconductors (HTSs) are enablers of extensive electrification for aircraft propulsion. Indeed, if used in electrical machines, HTS materials can drastically improve their performance in terms of the power-to-weight ratio. Among the different topologies of superconducting electrical machines, a flux modulation machine based on HTS bulks is of interest for its compactness and light weight.

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To determine whether families would make use of a pediatric-specific inpatient hospice facility for end-of-life care for children. Location of end-of-life care and death are important considerations when treating children with life-limiting conditions. There is very limited research on utilization of an inpatient hospice facility for end-of-life care if a pediatric-specific facility is available.

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Superconducting YBa2Cu3Oy (YBCO) foams were prepared using commercial open-cell, polyurethane foams as starting material to form ceramic Y2BaCuO5 foams which are then converted into superconducting YBCO by using the infiltration growth process. For modelling the superconducting and mechanical properties of the foam samples, a Kelvin-type cell may be employed as a first approach as reported in the literature for pure polyurethane foams. The results of a first modelling attempt in this direction are presented concerning an estimation of the possible trapped fields (TFs) and are compared to experimental results at 77 K.

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High-Temperature Superconductors (HTS) considerably accelerate the development of superconducting machines for electrical engineering applications such as fully electrical aircraft. This present contribution is an overview of different superconducting materials that can be used as magnetic screens for the inductor of high specific power electrical machines. The impact of the material properties, such as the critical temperature (Tc) and the critical current density (Jc), on the machine performances is evaluated.

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High-temperature superconducting (HTS) bulks can be used in electrical applications. Experimental characterization of large-size HTS bulks is a tricky issue. The relevant parameters for their application were directly measured in this study.

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ACR Appropriateness Criteria Tinnitus.

J Am Coll Radiol

November 2017

Tinnitus is the perception of sound in the absence of an external source. It is a common symptom that can be related to hearing loss and other benign causes. However, tinnitus may be disabling and can be the only symptom in a patient with a central nervous system process disorder.

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ACR Appropriateness Criteria Sinonasal Disease.

J Am Coll Radiol

November 2017

Imaging of sinonasal pathology may occur for assessment of rhinosinusitis or mass lesions. Rhinosinusitis is prevalent in up to 16% of the US population with annual economic burdens estimated at 22 billion dollars. Rhinosinusitis is characterized as acute or chronic based on symptom duration; if four or more episodes occur annually, the term recurrent acute rhinosinusitis (RARS) is used.

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ACR Appropriateness Criteria Plexopathy.

J Am Coll Radiol

May 2017

MRI without and with contrast is the most accurate imaging method to determine whether a process is intrinsic or extrinsic to a nerve of the brachial or lumbosacral plexus. However, there are no Current Procedural Terminology codes to correspond to imaging studies of the brachial or lumbar plexus discretely. This assessment uses "MRI of the brachial plexus" or "MRI of the lumbosacral plexus" as independent entities given that imaging acquisition for the respective plexus differs in sequences and planes compared with those of a routine neck, chest, spine, or pelvic MRI, yet acknowledges the potential variability of ordering practices across institutions.

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Background: PET/CTA was used to evaluate the effect of cholesterol crystal emboli (CCE) on muscle injury. Cholesterol crystals (CCs) released during plaque rupture travel downstream and lodge in muscle triggering inflammation and tissue injury.

Methods: Thigh muscles in three groups of rabbits (n = 22) were studied after intra-arterial injection of CCs, Group I (n = 10); polystyrene microspheres, Group II (n = 5); or normal saline, Group III (n = 7).

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Neuroimaging plays an important role in the management of head trauma. Several guidelines have been published for identifying which patients can avoid neuroimaging. Noncontrast head CT is the most appropriate initial examination in patients with minor or mild acute closed head injury who require neuroimaging as well as patients with moderate to severe acute closed head injury.

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Patients presenting with myelopathic symptoms may have a number of causative intradural and extradural etiologies, including disc degenerative diseases, spinal masses, infectious or inflammatory processes, vascular compromise, and vertebral fracture. Patients may present acutely or insidiously and may progress toward long-term paralysis if not treated promptly and effectively. Noncontrast CT is the most appropriate first examination in acute trauma cases to diagnose vertebral fracture as the cause of acute myelopathy.

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Background: Human and feline head and neck squamous cell carcinoma (HNSCC) share histology, certain molecular features, as well as locally aggressive and highly recurrent clinical behavior. In human HNSCC, the presence of significant hypoxia within these tumors is considered an important factor in the development of a more aggressive phenotype and poor response to therapy. We hypothesized that feline head and neck tumors, particularly HNSCC, would exhibit hypoxia and that ⁶⁴Cu-diacetyl-bis(N4-methylthiosemicarbazone) (Cu-ATSM) positron emission tomography/computed tomography (PET/CT) would permit detection of intratumoral hypoxia.

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Sinonasal imaging is performed in 2 major clinical scenarios: inflammatory rhinosinusitis or suspected mass lesion. Rhinosinusitis affects more than 16% of the US population annually. It poses an immense economic burden, accounting for more than 26 million outpatient visits annually and costing more than $4.

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We applied a multi-modal imaging approach to examine structural and functional alterations in the default-mode network (DMN) that are associated with Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI), a transitional phase between healthy cognitive aging and dementia. Subjects included 10 patients with probable AD, 11 patients with aMCI, and 12 age- and education-matched normal controls (NC). Whole-brain resting-state functional, diffusion-weighted, and volumetric magnetic resonance imaging (MRI) data as well as 18F-fluorodeoxyglucose-based positron emission tomography (FDG-PET) data were acquired.

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Primary Objective: To evaluate brain activation patterns of asymptomatic athletes with a history of two or more concussions.

Research Design: A paired case-control design was used to evaluate brain activation patterns during cognitive performance in 14 athletes with a history of two or more concussions and 14 age- and sex-matched controls with no previous concussion.

Methods And Procedures: Percentage Blood-Oxygen-Level-Dependent (BOLD) change during an N-back working memory task was assessed in all participants.

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Purpose: Although breast dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) demonstrates high sensitivity for malignant tumor detection, a major limitation is the relative low specificity, resulting in many false-positive diagnoses of suspicious lesions (BI-RADS assessment of 4 or 5) in clinical practice and consequently producing a relatively low positive predictive value (PPV) for biopsies. The most enhanced areas in the malignant tumors show a typical washout (WO) kinetic feature for the postcontrast signal intensity time courses and also correlate with microvessel density. Benign proliferative breast diseases can also produce the WO curve, yielding an equivocal kinetic behavior for the benign lesions and rendering their diagnoses as suspicious lesions in clinical practice.

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Objective: This study evaluated effects of lipid lowering with ezetimibe on plaque burden and associated cholesterol crystallization and inflammation in a rabbit model of plaque disruption and thrombosis.

Methods And Results: Atherosclerotic rabbits (Group I, n=10 without; Group II, n=12 with ezetimibe, 1 mg/kg per day) were pharmacologically triggered for plaque disruption. Fluorodeoxyglucose positron emission tomography, RAM 11 macrophage staining, and serum inflammatory markers detected arterial inflammation.

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Background: Alzheimer's disease (AD) and mild cognitive impairment (MCI) affect the limbic system, causing medial temporal lobe (MTL) atrophy and posterior cingulate cortex (PCC) hypometabolism. Additionally, diffusion tensor imaging (DTI) studies have demonstrated that MCI and AD involve alterations in cerebral white matter (WM) integrity.

Objectives: To test if (1) patients with MCI and AD exhibit decreases in the integrity of limbic WM pathways; (2) disconnection between PCC and MTL, manifested as disruption of the cingulum bundle, contributes to PCC hypometabolism during incipient AD.

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Computed Tomography (CT) is used for the attenuation correction of Positron Emission Tomography (PET) to enhance the efficiency of data acquisition process and to improve the quality of the reconstructed PET data in the brain. Due to the use of two different modalities, chances of misalignment between PET and CT images are quite significant. The main cause of this misregistration is the motion of the patient during the PET scan and between the PET and CT scans.

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Error-free reconstruction of PET data with a registered CT attenuation map is essential for accurate quantification and interpretation of cardiac perfusion. Misalignment of the CT and PET data can produce an erroneous attenuation map that projects lung attenuation parameters onto the heart wall, thereby underestimating the attenuation and creating artifactual areas of hypoperfusion that can be misinterpreted as myocardial ischemia or infarction. The major causes of misregistration between CT and PET images are the respiratory motion, cardiac motion and gross physical motion of the patient.

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Background: It has been shown that plaque uptake of fluorodeoxyglucose is proportional to macrophage density. We tested the hypothesis that arterial thrombosis occurs in areas with high fluorodeoxyglucose uptake and that computed tomography angiography (CTA) can detect thrombi in vessels.

Methods And Results: Twenty New Zealand White rabbits were studied before and after atherosclerosis induction through de-endothelialization and a high-cholesterol diet; 14 were then thrombus triggered.

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Context: Contrast-enhanced magnetic resonance (MR) imaging provides better detail of the breast than either mammography or ultrasound imaging and can be a valuable adjunct to other imaging techniques, particularly for small lesions, in dense or augmented breasts and for treatment planning.

Objective: To illustrate some common technical problems encountered with MR imaging of the breast and present breast pathologies depicted with MR.

Results: Using a case-study approach, the authors discuss breast MR imaging difficulties related to hardware, software, technologist performance and patient cooperation.

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The cortical regions specialized in speech-language exhibit a left-right asymmetry, e.g., a larger cortical size in the left auditory cortex and Wernicke's area.

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